The present invention relates to releasable connectors for releasably connecting two elements together and is particularly although not exclusively concerned with a releasable connector for releasably supporting a load from the depending end of a cable.
In one method of launching an inflatable liferaft from the deck of a ship in an emergency, a packed uninflated liferaft is attached to a davit cable and is brought by the davit from a position on the deck to a position overhanging the side of the ship, in which position it is inflated and then boarded by evacuees. The liferaft is then lowered on the davit cable until it comes to rest on the water. The liferaft needs to be held secure to the end of the davit cable during launching but readily releasable from the cable when the liferaft takes up a self-supporting floating position on the water.
In prior British Patent Specification No. 910904, a releasable connector has been proposed which provides for automatic release of the liferaft from the davit cable when the liferaft enters the water and which also provides for manual release by an occupant of the liferaft in the event that the automatic release fails. During launching and lowering of the liferaft the connector is arranged to hold a safe position in which it will not automatically release and to be moved to a cocked position for automatic release by an occupant of the liferaft pulling on a release lanyard just prior to the liferaft entering the water. In the event that the automatic release fails when the liferaft enters the water an occupant of the liferaft can override the automatic release by pulling on the lanyard and with the connector only lightly loaded in this condition effect manual release.
Although the connector hitherto proposed has operated generally satisfactorily there are circumstances which although very remote can give rise to premature release of the liferaft from the davit cable. For example, the connector is arranged to be manually releasable only when lightly loaded as when the liferaft is floating on the water and is intended to be manually releasable in this situation only. With an inflated liferaft at the boarding position and carrying one occupant only, it is possible that the occupant could achieve premature release of the lightly laden liferaft by exerting a very heavy pull on the lanyard. This may be done for example in circumstances where the occupant fails to observe the instructions or accidentally pulls on the lanyard in an effort to maintain his balance when boarding the liferaft. There is also the possibility of the release lanyard becoming caught up or tangled in the folds of the liferaft during inflation of the liferaft, which could result in a pull on the lanyard sufficient to cause premature release of the connector.
Although the circumstances likely to give rise to premature release of a liferaft from a davit cable when using a releasable connector as hitherto proposed are remote it is an object of the present invention to provide a releasable connector which reduces still further the possibility of premature release of the liferaft from the cable.
According to the present invention, there is provided a releasable connector for releasably connecting together first and second elements comprising a support structure to which the first element is secured, a first securing member for releasably securing the second element to the support structure and mounted on the support structure for movement between a securing position in which it so cooperates with the support structure as to prevent the second element from releasing from the support structure and a release position in which it no longer prevents release of the second element from the support structure, a second securing member mounted on the support structure for movement firstly from a retention position in which it retains the first securing member in its securing position and prevents it from moving to its release position, to a drive position in which it no longer retains the first securing member in the securing position and in which it drivingly engages the first securing member and then in a driving movement from the drive position to a release position in which driving movement it drivingly engages the first securing member to cause displacement of the first securing member from the securing position to its release position, and means for moving the second securing member from its retention position to its drive position and from its drive position to its release position comprising a drive member which is mounted on the supporting structure, which is movable between a first stop position to which it is biased and a second stop position and which so engages the second securing member that when the drive member is moved in a first traverse from its first stop position to its second stop position against the biasing action it moves the second securing member from the retention position to the drive position and upon release returns under the biasing action to the first stop position without the return of the second securing member to the retention position and in a second traverse from its first stop position to its second stop position against the biasing action it moves the second securing member from its drive position to its release position thereby to move the first securing member from its securing position to its release position.
In an embodiment of the invention the drive member is so constructed and arranged as to cooperate with first and second ratchet teeth on the second securing member. The drive member in a first traverse engages with the first of the ratchet teeth to move the second securing member from its retention position to its drive position and in a second traverse engages with the second of the ratchet teeth to move the second securing member through its driving movement in which it moves the first securing member to its release position.
In an embodiment of the invention hereinafter to be described, the drive member is movable through its first and second traverses by manually exerting a pull on a lanyard connected to the drive member. The first and second securing members are preferably pivotally mounted on the support structure and the drive member mounted on the support structure for movement in an arcuate path about the pivotal axis of the second securing member.
In the embodiment of the invention hereinafter to be described, the first of the two elements to be connected together is the depending end of a davit cable and the second of the elements is in the form of a shackle bolt secured to one end of a liferaft to be suspended from the cable. The support structure is so shaped as to allow upward penetration of the shackle bolt into the support structure and the first securing member is so mounted on the support structure and so shaped that it is biased to its securing position by the downwardly directed force applied to it by the shackle bolt.
In the embodiment of the invention hereinafter to be described, the first and second securing members are coupled together by a coupling spring which in a first position to one side of a dead-center position holds the second securing member in the retention position and in a second position to the other side of the dead-center position urges the second securing member into its drive position. With the second securing member moved to its drive position by a first traverse of the drive member and with the load applied by the shackle bolt to the first securing member relieved, the drive from the coupling spring operating to the other side of its dead-center position moves the second securing member through its driving movement and the first securing member to its release position.
In operation, a first pull on the lanyard causes the drive member to move through a first traverse from its first stop position to its second stop position and by its engagement with the first of the ratchet teeth of the second securing member to pivot it from its retention position to its drive position in which it is out of locking engagement with the first securing member and in which it drivingly bears against the second securing member under the action of the coupling spring. Upon release of the pull on the lanyard the drive member returns to the first stop position, riding over the first of the ratchet teeth and leaving the second securing member biased by the coupling spring to its drive position in engagement with the first securing member. The drive member upon returning to the first stop position drops into engagement with the second ratchet tooth of the second securing member. Providing no further pull is applied to the lanyard the first securing member maintains support for the shackle bolt while the latter is subjected to a downward force created by the liferaft.
Upon the liferaft taking up a floating disposition on the water the downward force applied by the shackle bolt on the first securing member is relieved whereupon the latter pivots to its release position under the drive from the coupling spring operating to the other side of its dead-center position. In the event that the first securing member does not move automatically to its release position under the action of the coupling spring, release of the shackle bolt can then be manually effected by pulling again on the lanyard to move the drive member through a second traverse, thereby causing the second securing member to execute its driving movement in which it turns the first securing member to its release position for release of the shackle bolt.